Variable Ratio (VR) steering system

Bishop VR rack

Honda VSA (Vehicle Stability Assist) rack

Curved teeth on VR racks

Daimler Direktlenkung

ActivRak VR-rack details

Rack tooth surface has to be adjusted in order to achieve variable ratio. 

US3753378

FIG. 8 is a sectional view to a very much enlarged scale of the rack and pinion of FIG. 5a showing the particular features of contact between the rack and the pinion being a section through the centerline of the rack;

FIG. 9 is a plan view in diagrammatic form of the pinion and the rack showing the position of various section lines referred to in the description;